Mastering fluid flow to enhance user experience

By Mike Worth, Mark Buckingham and Ben Strutt
Find the authors
on LinkedIn:

Mike Worth

Consultant Simulation Scientist

Mark Buckingham

Senior Consultant Chemist

Ben Strutt

Head of Consumer Healthcare

Ice cream and blood are two things you probably don’t want to think about simultaneously. But both are full of organic proteins and fats and behave differently from a fluid like water when they’re pumped through tubes. Innovators sometimes think about these similarities when creating, for example, a novel ice cream dispenser or device that filters out platelets from donor blood .

How a substance flows is a vitally important consideration for many products, from foods to skincare to medical devices to household paints. Development teams need to keep in mind a wide range of flow behaviors (for example, flow through nozzles, non-Newtonian flow, and foaming) to hit the sweet spot: a positive user experience that makes a product stand out in a crowded market. This means thinking about the science of how liquids and gases behave (fluid dynamics), as well as how the product responds to user interaction.

Look at how the squeezable plastic ketchup bottle differs from the glass bottles that were standard before 1983. The new design completely changed the user experience – no more digging down into the bottle with a knife to get the ketchup flowing again. Things became even easier for ketchup lovers with the debut of the upside-down squeezable bottle – no more awkwardly storing ‘regular’ bottles upside down in the fridge.

Or think about how the experience of washing your hands changed after the arrival of the liquid soap dispenser. Instead of having to share the same bar of soap with others, people can now wash “without the soapy mess”, as Robert R Taylor, who introduced SoftSoap liquid soap, put it, and can take only as much soap as they need.

While the flow of some liquids is analogous to water, whose behavior is well understood, other substances behave in much more complicated ways, requiring in-depth analysis work to understand when designing new products. For example, the air bubbles in ice cream make it behave as a liquid foam. Ice cream’s flow will change depending on how you’re dispensing it: Push it at high pressure through a narrow channel or nozzle, and the air bubbles will be compressed, allowing more ice cream to flow through the nozzle at once. When the ice cream is returned to normal pressure, the air bubbles re-expand, and the ice cream returns to its original size. Because of this complex and variable behavior, designing a product to dispense ice cream relies on hands-on experiments… which can mean going through gallons of ice cream before you can create a design that works as intended. Only by conducting these experiments to understand ice cream’s behavior can you build the mathematical model required to effectively develop a high-performance machine.

While it’s a shame to use gallons of ice cream in the quest for a better product, it’s not an environmental disaster. But shipping water-based products around the world does contribute to fossil fuel consumption and climate change. Removing water from laundry detergent helps cut shipping emissions by reducing bulk and making shipping more efficient. But it also dramatically changes how detergent flows and gets used by consumers. For example, measuring out 10 ml more detergent than recommended likely wouldn’t have an impact if you’re using a product that’s mostly water. But being off by 10 ml when detergent is concentrated could make a big difference for your laundry. So, it’s vital to ensure that dispensing is accurate, which requires an understanding of flow.

There are so many flow behaviors that can affect a product’s design. For example, should a container for insecticide include a mechanism to avoid skin contact and spillage? How could a medical device for freezing tumors be redesigned to eliminate vapor locks without the use of heavy and bulky high-pressure gas cylinders? Is there a way to dispense foaming hand soap in a decorative pattern for a premium experience?

Getting the design right for a flowing substance can differentiate between a product that fails and one that creates an experience that shifts category norms and delivers breakthrough consumer delight.

References

Find the authors on LinkedIn:

Mike Worth

Consultant Simulation Scientist

Mark Buckingham

Senior Consultant Chemist

Ben Strutt

Head of Consumer Healthcare